[Bug libstdc++/101227] Clang++ fails to instantiate std::optional if nested type has a non-static data member initializer

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101227

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Yes. It's basically the same issue as PR 96645. Nested types and default member
initializers are not compatible with standard library wrapper types. Yet
another horrible corner of C++.